An electric fan which comprises an impeller and a casing is known. The impeller includes a plurality of blades and is configured to rotate by an electric motor. The casing includes abase which defines a receiving space to receive a stator and a rotor of the electric motor. In such an electric fan, a liquid such as water may enter into the receiving space from between an impeller body of the impeller and the base. In order to cope with this problem, Japanese Patent No. 3694224 (JP3694224), for example, proposes that a clearance be defined between a casing and an impeller of a centrifugal fan to form a labyrinth structure for blocking entry of a liquid into a receiving space.